<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>Circle Area</title>
</head>
<body>
<form action="/CircleAreaServlet" method="get">
  <label for="radius">请输入圆的半径：</label>
  <input type="text" id="radius" name="radius">
  <input type="submit" value="计算">
</form>
</body>
</html>
